填塞塑料以前的型腔准备包括_________、_________和_________,常用_分离剂涂布于石膏表面。
参考答案:去蜡;修整石膏模型;涂分离剂;藻酸钠
裸子植物比被子植物低等,是因为裸子植物( )
A.果实内有种子
B.没有果实,种子裸露在外面
C.胚珠的外面有子房壁保护
D.球果包被着果皮
The money collected should be made good use ________ the people who suffered a lot in the
earthquake.[ ]
A. of helping
B. to help
C. to helping
D. of to help